01 - Whisk egg yolks and granulated sugar in a heatproof bowl set over gently simmering water until pale and slightly thickened, about 3 to 4 minutes. Remove from heat and allow to cool slightly.
02 - Fold mascarpone cheese and vanilla extract into the yolk mixture until the consistency is smooth and creamy.
03 - In a separate bowl, whip cold heavy cream to stiff peaks. Carefully fold whipped cream into the mascarpone mixture until just blended.
04 - Combine espresso and coffee liqueur in a shallow dish. Briefly dip each ladyfinger into the coffee mixture for 1–2 seconds per side, without oversoaking.
05 - Arrange a single layer of dipped ladyfingers in a 9 x 9 inch baking dish. Spread half of the mascarpone cream evenly over the ladyfingers.
06 - Add another layer of dipped ladyfingers. Top with the remaining mascarpone cream and smooth the surface.
07 - Cover and refrigerate for at least 4 hours or overnight for optimal flavor and texture.
08 - Dust generously with unsweetened cocoa powder and garnish with dark chocolate shavings before serving, if desired.